1. Field of the Invention
The present invention relates, in general, to apparatus for measurement of forces and/or moments acting on rotatable members, such as vehicle wheels.
2. Description of the Art
Wheel load transducers are known for attachment to a vehicle wheel to measure torque, moments and forces applied to the wheel. Such transducers, as shown in FIGS. 16 and 17 and described in greater detail hereafter, are typically in the form of an annular member which is affixed at an outer peripheral portion to a rim adapter welded to the wheel rim. The adapter has a plurality of circumferentially spaced apertures which align with corresponding apertures in the outer periphery of the transducer for receiving bolts therethrough to fix to the transducer to the wheel rim.
The transducer also includes an inner annular portion which also has a plurality of circumferentially spaced apertures. A hub adapter containing a corresponding circumferential arrangement of apertures is mountable on the inner ring and fastened thereto. The hub adapter includes a standard hole arrangement for attachment to vehicle wheel bolt lugs.
A plurality of radial extending webs or beams interconnect the inner and outer portions of the transducer. Moments and forces exerted on the wheel are measured by sensors, such as strain gages, which are adhesively affixed to exterior surfaces of the webs or beams. Strain gages mounted on the inboard and outboard surfaces of the beams provide torque measurements. Strain gages mounted on the sides of the beams are positioned for providing steering and camber moments and lateral force measurements. This type of transducer is not capable of measuring vertical and fore and aft forces acting on the wheel.
Other more complex transducers are capable of measuring the three directional forces, torque, camber moment and steering moment. However, such wheel load transducers have required many output channels, such as up to twelve output channels to measure the three primary forces and three primary moments or torque exerted on a vehicle wheel. Further, all such transducers exhibit some degree of imperfection known as crosstalk. Crosstalk are measurement errors that occur when forces or moments are applied at directions at right angles to the desired measurement direction.
Thus, it would be desirable to provide a force and/or moment measurement device suitable for use with rotatable members, such as vehicle wheels, which is capable of obtaining force and/or moment measurements with a high degree of accuracy. It would also be desirable to provide such a measurement apparatus or transducer which minimizes crosstalk measurement errors between adjacent sensors. It would also be desirable to provide such a measurement apparatus or transducer which optimally locates the measurement devices or strain gages for more precise measurement. Finally, it would be desirable to provide such a measurement apparatus which has a minimal number of independent output data channels.